The present invention relates to an apparatus and method for dynamically blending two or more fluids to form a blended gaseous mixture which is delivered via a distribution header to one or more tools for chemical vapor deposition, including epitaxial film growth or similar layer deposition processes. Although the invention may have other applications, it is particularly applicable in semiconductor fabrication.
Semiconductor manufacturers often use a deposition gas mixture of trichlorosilane (SiHCl.sub.3) (TCS) and hydrogen (H.sub.2) for growth of thin films (e.g., epitaxial silicon) on silicon wafers. Such a mixture is usually obtained by sparging or bubbling H.sub.2 gas into TCS liquid held at a specified temperature in a bubbler apparatus. This apparatus delivers a H.sub.2 gas carrier stream saturated with TCS into a process tool used in semiconductor fabrication. However, since the stream must be saturated to ensure a consistent composition into the process tool, the bubbler must be located at close proximity to the process tool to avoid condensation in the customer's supply line (because condensation would affect the stream composition). Consequently, each tool typically has its own bubbler, which significantly increases capital expenditures required to handle TCS and reduces the available floor space in semiconductor fabrication facilities.
It is desired to have a delivery system and method which provide consistent composition of a blended gaseous mixture at a non-saturated condition (i.e., lower TCS dewpoint).
It is further desired to have a distribution header from which the blended gaseous mixture could be delivered to multiple tools, which would reduce floor space requirements and save capital.
It is still further desired to have the ability to provide a blended gaseous mixture to a variable number of process tools while maintaining consistent stream composition.
It is still further desired to have the ability to quickly manipulate the stream composition when end user requirements fluctuate.